Method for producing packaging units in a tubular bag-making machine

ABSTRACT

The invention relates to a method for manufacturing packaging units ( 20 ) in a tubular bag forming, filling and sealing machine, which method contains vertically conveying disk-shaped products ( 11 ), which lie one above the other in portion stacks ( 10 ), and wrapping them with a film web being conveyed parallel to the products by means of a film take-off device, wherein the film web, in order to form a film tube ( 12 ), is provided with a longitudinal sealed seam by means of a longitudinal sealing device and subsequently with transverse sealed seams ( 18 ) above and below the portion stack by means of a transverse sealing device ( 14 ) being driven by a drive device independently of the film take-off device and moving in the same direction as the film web while the sealing device contacts the film web for sealing purposes, the transverse sealing device carrying out a vertical movement relative to the film tube in the direction opposite the conveying direction of the film tube while the sealing device contacts the film tube for sealing purposes.

The invention relates to a method for manufacturing packaging units in atubular bag forming, filling and sealing machine, which method containsvertically conveying disk-shaped products, which lie one above the otherin portion stacks, and wrapping them with a film web being conveyedparallel to the products by means of a film take-off device, wherein thefilm web, in order to form a film tube, is provided with a longitudinalsealed seam by means of a longitudinal sealing device and subsequentlywith transverse sealed seams above and below the portion stack by meansof a transverse sealing device being driven by a transverse sealingdrive device independently of the film take-off device and moving in thesame direction as the film web while the sealing device contacts thefilm web for sealing purposes.

When manufacturing tubular bags, the film web initially being fed to amolding shoulder as a flat element is shaped, by means of the moldingshoulder, into a plastic tube which has an overlapping longitudinaljoint, and which serves for receiving products being conveyed to thefilm web in a fashion parallel thereto and lying one above the other ina portion stack. After the longitudinal joint has been sealed by meansof a longitudinal sealing device, transverse sealed seams are formed bymeans of a transverse sealing device for manufacturing a packaging unitthat in each instance receives one or more portion stacks lying onebehind the other in a row in the conveying direction.

With the disk-shaped products lying one above the other in a portionstack, it has in particular in the context of cookies and similar items,which have a cream filling between sandwich cookies, shown that tensilestresses arise in the film web due to the formation of the transversesealed seams, which tensile stresses give rise to radial stresses beingexerted on the cookies, causing a wedged pitch of the sandwich cookiesin the cream filling that is often still warm and soft at the time ofmanufacturing the packaging units and thus causing an undesireddeformation of the product.

One possibility of avoiding this undesired wedge effect, is to maintaina sufficiently large space between the portion stacks being arranged inthe film tube, in the conveying direction of the film web, when creatingthe transverse sealed seams, such that the tensile stresses that arisewhen creating the transverse sealed seams are reduced and thus theradial stress acting on the cookies also become correspondingly smaller.However, a corresponding reduction of the filling degree of theindividual packaging units and an increase in the consumption of filmweb are connected with this, such that, apart from a deterioration inthe productivity of the production device, an increase in themanufacturing costs is also the result.

The present invention is therefore based on the task of proposing amethod for manufacturing packaging units in a tubular bag forming,filling and sealing machine, which method allows for packaging that isgentle on the product at a high productivity of the production facility.

This task is solved by a method having the features of claim 1.

In the method in accordance with the invention, the transverse sealingdevice carries out a vertical movement relative to the film tube in thedirection opposite the movement direction of the film tube while thesealing device contacts the film tube for sealing purposes.

Owing to the fact that the transverse sealing device contacts the filmtube for sealing purposes, an accumulation of the film tube results fromthe superposition of the vertical relative movement, which takes placein the direction opposite the movement direction of the film tube, theaccumulation being located in the region between the transverse sealedseam and the portion stack being arranged above the transverse sealedseam. Said accumulation leads to the film tube remaining substantiallyfree of tensile stresses in the region of the lower end of therespective packaging unit and to a limp bag gusset being formed.

Hereby, it is ensured that by forming the sealing in the region of thetransverse sealed seam, tensile stresses are not induced in the filmtube, which stresses would give rise to undesired lateral forces beingexerted on the lower end of the portion stack.

Hereby, it becomes even possible to package easily deformable cookies,which means in particular sandwich cookies being provided with a creamfilling, immediately subsequently to the baking process, without makingsure that the cream filling is stable enough prior to packaging bycooling the cookies in between.

Since the film tube is preferably cut through in the region of thetransverse sealed seam, simultaneously to the transverse sealed seambeing formed, it is avoided that, due to the accumulation, increasedtensile stresses can arise in the region of the upper packaging end ofthe packaging unit being arranged below the transverse sealing device.

It proves to be particularly advantageous if the relative movement ofthe transverse sealing device is effected by means of a retardation ofthe vertical movement of the transverse sealing device since the filmweb can thus be conveyed continuously and at a constant speed in thetubular bag forming, filling and sealing machine by means of the filmtake-off device and the required relative movement can thus be effectedvia a corresponding kinematic control of the transverse sealing devicealone.

If the retardation of the vertical movement of the transverse sealingdevice, in a final phase of the contacting for sealing purposes, iseffected subsequently to an at least partially material connection offilm web portions that rest against one another, via the contacting forsealing purposes, a sufficiently high heat transfer into the film tubecan be effected in order to exploit a small plastic deformation of thefilm tube for supporting the formation of a limp bag gusset of thepackaging unit.

In order to preclude an application of force on the portion stack in theconveying direction of the film tube owing to the vertical relativemovement of the transverse sealing device, it is advantageous if themovement distance s that is covered by means of the relative movement ofthe transverse sealing device is smaller than the space a between thetransverse sealing device and the portion stack being arranged above thetransverse sealing device.

In the following, a preferred embodiment of the invention is explainedwith the aid of the drawings.

In the figures:

FIG. 1: shows a transverse sealing device in a starting phase ofcontacting the film tube for sealing purposes;

FIG. 2: shows the transverse sealing device being illustrated in FIG. 1in a final phase of contacting the film tube for sealing purposes.

FIG. 1 shows a lower end of a film tube 12 being formed in a tubular bagforming, filling and sealing machine for wrapping disk-shaped products11 lying one above the other in a portion stack 10. The film tube 12, bymeans of a film take-off device not being illustrated in more detail inFIG. 1, is conveyed in the vertical conveying direction 13 to atransverse sealing device 14, which comprises two sealing tools 15, 16being driven via a movement transmission that is not illustrated in moredetail, such that the same rest, with sealing surfaces 17, against thefilm tube 12 being arranged between the sealing tools 15, 16 whilecontacting the film tube for sealing purposes, said contact beingillustrated in FIG. 1.

Outside of the sealing phase being illustrated in FIG. 1, the sealingtools 15, 16 are in a portal position which is illustrated in FIG. 1 indash and dot lines, and in which position the sealing tools 15, 16 aremoved apart, such that the film tube 12, with the products 11 beingreceived therein, can pass through the sealing tools 15, 16 of thetransverse sealing device 14.

The movement drive of the sealing tools 15, 16 is formed such that thesealing tools 15, 16, in their sealing position being illustrated inFIG. 1, are moved, by means of a drive device not being illustrated inmore detail, in the conveying direction 13 of the film tube 12 whilecontacting the film web for sealing purposes. Afterwards, the sealingtools 15, 16 are moved back into the portal position and around themovement path being performed in the conveying direction 13 duringcontacting for sealing purposes in the direction opposite the conveyingdirection 13 of the film tube 12, in order to be transferred, in asubsequent sealing process for creating a transverse sealed seam 18,into the sealing position being illustrated in FIG. 1 again.

In the sealing position, the film tube 12 is cut through in the regionof the transverse sealed seam 18 by means of a cutting device 19 beingintegrated into the transverse sealing device, such that a packagingunit 20 being defined in its length by two adjacent transverse sealedseams 18 is torn off from the film tube 12.

The products 11 being illustrated in FIG. 1 by way of example aresandwich-like cookies, which receive a cream filling 23 betweensurrounding cookies 21 and 22. At the time of the manufacturing of thepackaging units 20, the cream filling 23 of the products 11 being fed tothe tubular bag forming, filling and sealing machine immediately after abaking process is still relatively soft, such that radial stressesacting on the sandwich cookies 21, 22 can easily lead to a deformationor to the cream filling 23 oozing out of the product 11.

As it can be comprehended with the aid of FIG. 1, owing to the sealingprocess, tensile stresses arise in the film tube 12 in the region of abag gusset 24 being formed between the transverse sealed seam 18 and theportion stack 10 of the products 11, which tensile stresses give rise toradial stresses F acting on a product boundary region 25 being oppositeto the transverse sealed seam 18, said stresses being able to cause awedged pitch of the sandwich cookies 21, 22 with respect to each otherwhen a critical size has been reached and if the cream filling 23 isstill soft, and thus being able to cause a corresponding productdeformation.

As it is illustrated in FIG. 2, the sealing tools 15, 16 of thetransverse sealing device 14, in a final phase of the contacting forsealing purposes, carry out a relative movement subsequently to an atleast partially material connection of film web portions 28, 29 thatrest against one another, for forming the transverse sealed seam 18,said relative movement having a movement path s, in order to move thesealing tools 15, 16 from the starting phase of the contacting forsealing purposes being illustrated in FIG. 2 in dash and dot lines inrelation to the film tube 12 in the direction opposite the conveyingdirection 13 of the film tube 12.

In the present case, said relative movement is carried out by aretardation of the transverse sealing device 14 being moved in the samedirection as the film tube.

As it becomes clear from FIG. 2, the formation of tensile stresses inthe bag gusset 24 and of radial stresses F that reach the critical sizecan be prevented in that, owing to the relative movement of thetransverse sealing device 14, a limp form of the bag gusset 24 isachieved.

As it can further be seen from FIG. 2, the movement distance s beingcovered by means of the relative movement of the transverse sealingdevice 14 is smaller than the space a between the transverse sealingdevice 14 and the portion stack 10 being arranged above the transversesealing device 14.

In order to support the bag gusset 24 being formed in a defined fashionat the transverse sealed seam 18, in the case of the illustratedexemplary embodiment, folding pushers 27, 28 are provided in eachinstance above and below the transverse sealing device 14, beingpivotable into the film tube 12 at an angle to the conveying direction13 of the film tube 12, and allowing for a defined formation of a gussetfold, such that the film web portions lying opposite to one another, inthe region of the bottom gusset, lie one above the other in a fanfoldfashion and such that a correspondingly defined formation of thetransverse sealed seams is possible.

1. A method for manufacturing packaging units in a tubular bag forming,filling and sealing machine, said method comprising: verticallyconveying disk-shaped products lying one above the other in portionstacks; wrapping the portion sacks with a film web conveyed parallel tothe products by a film take-off device; forming a longitudinal sealedseam in the film web to form a film tube using a longitudinal sealingdevice, said film tube moving in a conveying direction; and formingtransverse sealed seams in the film tube above and below each portionstack using a transverse sealing device driven by a drive deviceindependently of the film take-off device and moving in the samedirection as the film tube while the sealing device contacts the filmweb to form each transverse sealed seam, wherein the transverse sealingdevice moves vertically relative to the film tube in a directionopposite the conveying direction of the film tube while the sealingdevice contacts the film tube to form each transverse sealed seam. 2.The method according to claim 1, in which the relative movement of thetransverse sealing device is effected by means of a retardation of thevertical movement of the transverse sealing device.
 3. The methodaccording to claim 2, in which the retardation of the vertical movementof the transverse sealing device, in a final phase of the contacting forsealing purposes, is effected subsequently to an at least partiallymaterial connection of film web portions that rest against one another.4. The method according to claim 1, in which the movement distance sthat is covered by the relative movement of the transverse sealingdevice is smaller than the space a between the transverse sealing deviceand the portion stack of the products being arranged above thetransverse sealing device.